<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			
			var a = 123
			var _name = "zhangsan"
			
			var b = "123"
			console.log(b)
			console.log(typeof b)
			b = 123;
			console.log(b)
			console.log(typeof b)
			
			c = "hello"
			console.log(c)
			console.log(typeof c)
			
			console.log(d)
		</script>
	</body>
</html>
